Q&A - P5 Math
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Superbugs:
HiOn Mon, M read 52 pages of a book. On Tues, he read 2/5 of the remaining pages. If he still had 1/3 of the book left to be read, how many pages were there in the book?
I am unable to draw the model here but it goes like this:
52 pages (Mon) + 2/5 (Tues) + 3/5 (unread)
So 1/3 = 3/5 unread
Hence 2/3 = 52 pages + 2/5 read
I get common denominator of 15, hence
10/15 = 52 pages + 6/15, so
4u => 52 pages
15u=> 195 pages but answer is 117 pages where becos 1/3 = 3/5 unread, 2/3 must be = 6/5 read
Hence 52 pages = 4/5 read
9u => 117 pages
Why is that so?
the MD approach ...![](\"http://i56.tinypic.com/xeig7d.jpg\")
http://i56.tinypic.com/xeig7d.jpg\">
cheers. -
Superbugs:
Easier to do this question using model method.On Mon, M read 52 pages of a book. On Tues, he read 2/5 of the remaining pages. If he still had 1/3 of the book left to be read, how many pages were there in the book?
52 + XX ( read) + XXX( unread) = book
XXX ( unread) = 1/3 of book
2/3 of book = XXXXXX
therefore 52 + XX = XXXXXX
4X = 52
X= 13
Total pages in the book = 52 + 5X = 52 + 5(13) = 117 -
I still don’t get yours - Mathizzzfun!
However my DD can solve it easily so I rest my case!
Tks to all! -
pixiedust:
Ah, yes! I managed to get the correct answer, thanks piggylalala!
You're welcome
All the best for the PSLE next year. -
Hi,
was lost in dealing fractions / %. Pls help on the following qs:
1. At a toy fair 40% of those present were boys . 8/15 of the remainder were girls & the rest were adults. There were 480 more boys than adults. How many more children than adults were there at the toy fair?
2. Last mth, David use $840 of his salary to buy a laptop. He spent 1/8 of the remaining salary on rent, $400 on food & saved the rest. The amount that he spent on food was $20 less than that spent on rent.
a. What was his salary?
b. What % of his salary did he save?
3. Larry spent $60 less than 5/8 of his money on a MP3 player & $25 more than 7/9 of his remaining money on assessment books. After buying the assessement books, he still had $10 left.
a. How much money was left after Larry bought the MP3 player but before he bought the assessment books?
b. How much money did Larry have at first?
TIA -
Need help on this question!
There are 60% as many blueberry muffins as banana muffins and 20% more chocolate muffins than the blueberry muffins. What is the ratio of the number of banana muffins to the number of chocolate muffins? -
Superbugs:
HiNeed help on this question!
There are 60% as many blueberry muffins as banana muffins and 20% more chocolate muffins than the blueberry muffins. What is the ratio of the number of banana muffins to the number of chocolate muffins?
Blueberry : Banana = 60 : 100 = 3:5 -- (1)
Blueberry : Chocolate = 100 : 120 = 5:6 -- (2)
(1)x5, (2) x 3
Blueberry : Banana: Chocolate = 15 : 25 : 18
cheers. -
jtparent:
HiHi,
was lost in dealing fractions / %. Pls help on the following qs:
1. At a toy fair 40% of those present were boys . 8/15 of the remainder were girls & the rest were adults. There were 480 more boys than adults. How many more children than adults were there at the toy fair?
TIA
1. Boys = 40%, Girls + Adults = 60%
Girls = 8/15 x 60% = 32%, Adults = 60% - 32% = 28%
480 more boys than adults, so 40$ - 28% = 12% = 480, 1% = 40
Total children = 100% - 28% = 72%
72% - 28% = 44% = 44 x 40 = 1760
there were 1760 more children than adults.
cheers. -
jtparent:
HiHi,
was lost in dealing fractions / %. Pls help on the following qs:
2. Last mth, David use $840 of his salary to buy a laptop. He spent 1/8 of the remaining salary on rent, $400 on food & saved the rest. The amount that he spent on food was $20 less than that spent on rent.
a. What was his salary?
b. What % of his salary did he save?
TIA
2. Amount spent on rent = 1/8 remaining salary = $400 + $20 = $420
So, total remaining salary (after spending $840) = 8 x $ 420 = $ 3360
a. Salary = $840 + $3360 = $ 4200
b. .. I think you can complete this
cheers. -
jtparent:
HiHi,
was lost in dealing fractions / %. Pls help on the following qs:
3. Larry spent $60 less than 5/8 of his money on a MP3 player & $25 more than 7/9 of his remaining money on assessment books. After buying the assessement books, he still had $10 left.
a. How much money was left after Larry bought the MP3 player but before he bought the assessment books?
b. How much money did Larry have at first?
TIA
for this question.. work backwards..
After spending 7/9 remaining + $25 --> $10 left
So, $10 + $25 = $35 = 2/9 remaining money.
Money remaining (after spending on MP3) = 35/2 x 9 = $ 157.50
MP3 player = 5/8 of Larry's money - $60
Money remaining (after buying MP3) = 3/8 of Larry's money + $60
3/8 of Larry's money = $157.50 - $60 = $97.50
Larry's money = $ 97.50/3 x 8 = $ 260
cheers.
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